BACKGROUND AND OBJECTIVE: Stenotrophomonas maltophilia is known as an emerging bacterium in the world, associated with a wide range of diseases. The aim of this study was to investigate the virulence factors of these bacteria including extracellular enzymes, ability to form biofilm and rpfF gene involved in quorum sensing.

METHODS: This cross-sectional study was conducted using urine samples, blood and sputum samples, swab samples of oxygen manometer system and tap-water of hospitals as well as dental suction. Bacteria identification was done using culture methods and biochemical tests and to confirm the existence of bacteria, presence of 23S rRNA gene was assessed using real-time PCR method. Isolates were studied in terms of gelatinase, hemolysin, hyaluronidase, lecithinase, lipase and protease enzymes using phenotypic method and biofilm formation using microplate method. Moreover, existence of rpfF gene in isolates was investigated using PCR method.

FINDINGS: 100% of isolates contained rpfF gene. Most isolates contained gelatinase (90%), hemolysin (85%), protease (75%), lecithinase (90%), lipase (75%) and hyaluronidase (100%) enzymes. Biofilm formation was not observed in 15% of isolates; 45% of isolates had weak power of biofilm formation; 40% of isolates had moderate power of biofilm formation and none of the isolates had strong power of biofilm formation. Correlation between hemolysin and lipase, hemolysin and lecithinase, and lecithinase and lipase variables was significant.

CONCLUSION: Results of the study demonstrated that bacteria isolates contained various virulence factors including rpfF gene that produce diffusion signal factor which  is essential for quorum sensing and were highly capable of producing extracellular enzymes and forming biofilm.